Apparatus for producing wood particle boards



July 23, 1963 E. GRE-EEN 3,093,781

APPARATUS FR PRUDUCING WOEJD PHRTICLE BRDS Filed Jam. 18. 196@ 2Sheets-Sheet I.

Jul? 23, 1963 E. GRETEN 3,098,781

APPARATUS EUR mummia: woon PARHGLE' Roms Filed Jan. 18, 1960 2Sheets-Sheet 2 United States Patent O 3,698,781 APPARATUS FOR PRODUCENGWGOD PARTICLE BOARDS Ernst Greten, Springe, near Hannover, Germany,assigner to Metallwerk Bahre KG., Springe, Deister, Germany Filed Jan.18, 1960, Ser. No. 2,873 1 Claim. (Cl. 156-373) This invention relatesparticularly to the method and apparatus for producing wood particleboards.

This application is a continuation-impart of my application Serial No.694,975, tiled November 7, 1957, now Patent No. 3,028,287, entitledApparatus for the Manufacture of Chipboards.

An object yof the invention is to provide an apparatus and method forproducing wood particle boards in a continuous operation, the upper andlower surfaces of which are composed of finer flakes, the inner portionor core being composed of coarser wood particles. These particles `arenot separated into layers of liner and coarser particles, but aregraduated in size from outer surfaces to an inner or central zone orcore. Thus the nest particles will be located adjacent the upper andlower sur- 'faces of the mat. Such Wood particle :or ake boards may, bysubsequent operations, be provided with veneers, paper covers, orplastic overlay on their opposite at surfaces.

Anotheriobject of the invention lis to provide an improvement in theeconomy of manufacturing wood particle boards.

An -additional object is the production of particle lbioards in acontinuous operation wherein the wood particles are lirs-t separated4according to coarseness. Following such separation, an adhesive,preferably in liquid form (although solid forms of ladhesive are notexcluded) is mixed with each of the several grades of wood particles indifferent amounts. The largest amount of adhesive is mixed with woodparticles having the largest supercies; the next largest amount ofadhesive is mixed with wood particles having the next largestsuperficies; Iand so on until the minimum amount of adhesive is mixedwith the wood particles having the smallest superlicies.

Yet another object is to provide an apparatus and methtod formanufacturing wood particle boards whereby the particles are evenlydistributed wiclthwise onto a moving conveyor so that the thickness willbe the same along rthe entire length and width of the board. The boardis subjected to various operations, such as heating and presstruction,etc.

An -additional object is to provide an air laid mat of lthe type aboveset forth, employing the present process or method in which the woodparticles are laid on a moving conveyor in a pla-ne or planes parallelto the face of the conveyor, in the same` manner that a sheet of papergravitates to a surface located below the same.

Other objects will appear hereinafter throughout the (specification. Y

Referring to the drawings:

FIG. 1 is a vertical section partly in full lines of the apparatus forseparating wood particles according to size, and the means for applying:adhesive thereto while so separated;

lFIG. 2 is a vertical section talQen on the line 2-2 of FIG. l;

FIG. 3 is a View of the air laid mat vforming mechanism, shown partly infull lines and partly in vertical section;

FIG. 4 is a top plan View of the structure shown in FIG. 3; g

PIG. 5 is a sectional view taken on the line 5 5 of FIG. 3;

FIG. 6 is la horizontal section taken on the line 6-6 of FIG. 5; and

FIG. 7 is a vertical sectional view, partly broken away, of the particleboard as it leaves the mat forming conveyor prior to pressing and otherfinishing operations.

Wood particle boards are produced from non-chemically processed dry woodparticles mixed with an adhesive, either natural or synthetic, Wet ordry, although a dry adhesive is preferred. In some processes chemicaltreatments may be used although such is not the preferred process in theproduction of particle boards.

The basic materials from which particle boards are produced may bedescribed as follows:

Chips, which are Wood particles used in pulp manufacture;

Flakes, which are mechanically produced sliced wood particles (similarin grain direction to sliced veneers), generally having less than 3/10inch thickness, and are relatively greater in length than width;

Ribbons, which are wood particles of the desired thickness, and whichvary as to length, but Whose length exceeds their abili-ty to retain astraight form. Examples of these include shavings from hand planing, cutparallel Eto the grain ot the wood. Excelsior is another example ofribbon cut material.

Shavings are the Wafer-likte Wood particles cut by rotary headpower-driven planers. These are characterized by thinness, great width,short length, and ruptured bers.

Spliuters are wood particles somewhat similar in appearance to brokentoothpicks, with cross sectional dimensions (of -a usual width of lessthan 1/s inch) and are of relatively greaterlength than width.

Wood particles also include some iines that are usually separated fromother wood particles, some of which, however, nd their way into the massof wood particles as they move from one station to yanother in thecourse of the various processing steps referred to hereinafter.Fiberboard -is distinguished from thevwood particle board which is theproduct of the method and apparatus of this invention by the degree ofiiberization. Fiberboard is `a product composed of separated wood fibersand lignin, formed` from a water or air suspension into a mat. The matafter treatment has interlaced tibers bonded principally lbyplasticizing the lignin in the presence of heat and pressure. Theadhesion of the interlaced bers may be augmented by resins, waxes, andasphalt compounds.

Fiberboard also includes hardboard and softboard. Hardboard hals a highdensity with a specific gravity of 0.80 or greater, while softboardwhich retains its porosity 3 is of low density and has a specic gravityof lfrom about 0.20 to 0.50.

Generally speaking, the process and apparatus of this invention relatesto :the production of particle boards wherein the dimensions of the woodpa-rticles from wo'odworking equipment have been at least partiallycontrolled. The length and thickness of the particles can normally becontrolled by the primary wood cutting operation, and la secondaryreduction of lthem will pnoduce the desired shape by regulating theparticle width and by furthe-r modifying the length thereof. Some of theparticles are made from standard Woodworking equipment, normally afterscreening Ito remove lines and oversized material without furtherreduction. However, other wood particles, when using a mixture lof woodshavings land wood flakes, are sometimes subjected to a secondaryreduction, especially in order to reduce the width of the particles bythe use of hammer mills. Additionally, hammer mills are used to preparethe wood particles `from small sized solid pieces of wood by grinding,breaking =or tearing the wood, in which oase the resulting chips aremostly coarse and splint/ered. Preliminary reduction of the wood issometimes carried on in knife hogs. Particle size from hammer mills willdepend upon the peripheral speed, the clearance of irnpellers, and .theclearance @between breaker plates or impellers.

Engineered particles may lbe produced by special cutting machines inorder to produce particles with their lgrain axes parallel to theirlength. Wood particle manutacturing equipment will cut the particles toa predetermined length and thickness either by using disc type cutters,cup or ring type cutters, or cylindrical cutters. A secondary reductionof the wood particles to a predetermined width and sometimes length,lalthough the latter is not usually resorted to, is normallyaccomplished in hammer mills or in wing beater mills.

While this invention is not concerned with a particular type of particleor flaking machines, it may be stated that particle Ithickness cannormally be controlled by both iknife protrusion .and the forward speedof the raw material.

It will be appreciated that the type of cutting machinery best suited toa particular particle board process is, of course, dependent upon theraw material available, the type of process, the desired properties inthe nished board, and the allowable manufacturing costs.

It will Ibe further understood that the hereinafter described apparatusand method may be used in the production of various finished products,such as furniture, corestock for plastic overlaid material, corestock4for vene-er, decorative interior panelling for housing, doors, board totake the place of plaster board in housing constructions or dwellings,structural construction members, etc. In fact, the residential buildingindustry, which consumes about 70% of all the lumber manufacturing inthe United States, is the greatest potential market :tor particle boardsproduced in accordance with `this invention. Such particle boards vareequivalent to or are in most cases superior to previously usedmaterials, and additionally show an over-all economic advantage. Suchparticle boards, -as produced by the present apparatus and method,exhibit all lof the better characteristics of more expensive materialsused in the residential building industry today, i.e., greater strength,better adaptation for receiving nails, screws or other metal objects,and the yability to retain the same in place.

Particle boards have been shown in the prefabricated iield, wheregypsum, plywood, and other products are popularly used in stressedstrain construction, to reduce yshipping costs. It is possible whenusing particle boards of the type noted above .to provide lfull wallsections that have been treated for decay, water, vermin, and to be tireresistant.

Raw material such as logs cut to size or pieces of wood refuse products,Ias indicated above, may be used. In a typical installation, however,raw material consisting of small logs, say from 6 to l0 inches indiameter, land about 3 feet long, are initially processed by beingsubjected in such apparatus to Ian automatic cut-olf saw. It is then tedto a flak-er 'where the cut off pieces or chunks are cut into particles,suchas flakes. These particles are then sent to a surge bin, thence to ahammer mill, thence to a jet dryer, thence to a screen, thence to asu-rge bin for dry material. These machines have not been shown, but are`known in the art. lFrom the surge bin for dry material the Woodparticles are deposited on a movable conveyor shown in FIG. 1 by thenumeral 10 from Iwhich they are deposited through an .opening lor hopper12 to the separating chamber 14. Here 'they are subjected to fa blast ofair issuing from the fan 16 through the screen 13 to the column ofparticles which fall by gravity into the interior 20 of the separatingchamber 14. The very light material and excess air is withdrawn throughthe exit 22.

The wood particles A according to their density, i.e. weight land size,fall into .one of the three bins 24', 26 or 28. It will be lnoted thatin accordance with IFIG. l these bins may be of diierent size, or vanesor valves (not shown) may be mounted in the upper inlet portions of eachto permit entrance of material in regulated amounts, the bin size beingin accordance with the amount of material to be received.

From the bins the material gravitates to the automatic gluing machineindicated by the numeral 30. Adhesive of any suitable type, in eithersolid or liquid form, is deposited on the material within the gluingmachine, although it is preferred to spray the glue in liquid onm on thematerial. The sprayers are indicated diagrammatically by the numerals32, 34, 36. The purpose .of separating lthe flakes according to size isto enable them to be sprayed with varying amounts of glue. Por instance,the smallestrwood particles as they move from the bin 24 to the `gluemachine 30 are directly sprayed with the smallest quantity of glue orother adhesive; the sprayer 34 at the same time spraying a larger amountof glue on the llakes which emerge trom chute 26,V while simultaneouslythe greatest -amount of glue is sprayed by sprayer 36 on the largestwood particles in the bin 28.

'Ihe particles `with glue on them are continually turned and ted by aworm, shown in dotted lines by the reference numeral 38', that rotateswithin the gluing machine 30 that is rotated by shaft l40v from asuitable source of power (not shown) until the material reaches the leftend of the gluing machine, whereupon it lfinds its way through the exit42 to the conveyor 44. Aft this time the several grades of material havebeen re-mixed with each other.

As distinguished from the berboard specific gravity noted above, theparticle boards can be produced with from 0.50 to 0.70 specific.gravi-ty, although the density will be in higher ranges if a highproportion of hardwoods is used i-n the manufacture.

Actually, there may be two structures of the type shown Iin FIG. 1, or asingle combined separator and gluing machine may be used which feedsonto separate conveyors 44. Inasmuch as the present invention is notconcerned with the number of separators and glue machines used, or themanner of conveying the glued material after it leaves the gluingmachine, one such machine has been shown in FIG. l, but parts of twogluing machines as well as two conveyors have been shown forillustrative purposes at 44 in FIG. 3, merely as examples of thedifferent ways in which the material may be conveyed from the gluingmachine or machines to the air laid mat forming mechanism. It will beunderstood that one or more conveyors are optional, and that other meanssuch as a gravity feed (not shown) may be used.

As the material, i.e., the glued impregnated wood particles reach theend of the conveyors 44, as indicated in FIG. 3, they drop by gravitythrough chutes 46 and 48 into the mat forming mechanism or chamber 50.This mat forming mechanism, as shown in FIGS. 3 and 4, is an elongatedgenerally rectangular chamber. As the material drops by gravity, thelightest particles, indicated at A1, fall by gravity at opposite ends ofthe chamber onto the moving belt 52, which occupies the lower open orbottom portion 54 of the chamber 50. The texture of the mat graduallybecomes more coarse toward the center or core, although no distinctlayers are formed, the finer flakes being shown at A1, the less coarsewood particles at A2, and the coarsest or heaviest wood particles at A3.However, as stated heretofore, there are no distinct layers, the woodparticles gradually becoming heavier and larger towards the center orcore of the mat, whereby the innermost or core portion of the matcontains the coarsest particles, the lightest particles being depositedto form the upper and lower surfaces of the mat.

This distribution of the wood particles on the travelling belt 52 whichmoves from left to right :is brought about by forcing streams of airfrom the fan 56, which is mounted on the casing by any suitablesupporting means, not shown. This fan may be of various types, butpreferably is of the centrifugal type, the air being dischargeddownwardly through the conduit 58. Adjacent the lower end of thisconduit is a sleeved conduit 60 which is adjustable vertically, asindicated in FIG. 5. Conduit 60 is provided with slots 62 and with abolt -64 having a nut 66 on each end thereof, which latter may betightened in order to hold the conduit 60 in adjusted verticalpositions. However, any other suitable means may be provided byadjusting the lower sleeved conduit 60. The latter is preferablyprovided with vanes for directing the material in divergent pathsthrough horizontal conduit portions 70 and 72. These portions preferablyextend the entire width of the mat forming chamber 50, and each of themmay be provided with adjustable valves shown at 74 and 76, respectively.The air stream issuing from the exits 7S and 80 engages the glueimpregnated particles as they fall by gravity and forces them to bedeposited on conveyor 52 in accordance with the weights of theindividual particles, so that the initially deposited particles A1 atthe left of iFIG. 3 form the lowest portion of the mat. As the conveyorbelt 52 moves to the right, heavier and heavier particles are added tothe initially deposited particles until the heaviest particles A3 aredeposited as they fall from the chute 46. As the belt continues itsrightward movement, the heaviest flakes which fall from lchute 48 formthe remainder of the core of the mat, following which less heavyparticles A2 are deposited in graduated amounts until the lightestparticles, or those corresponding to the particles in engagement withthe belt, form the top surface of the air laid mat A4.

By reference to FIG. 4 it will be noted that the ends of the mat formingchamber 50 are provided with converging walls indicated at 82 and 84 towhich pairs of conduits 86, 83 and 90, 92, respectively, are connected.These conduits are provided with valve means indicated by referencenumeral 94 by which the amount of return air in each of them may beindividually regulated. It will be understood, however, that thesevalves may be placed anywhere in these conduits or they may be omittedentirely. The pairs of return conduits are connected to the fan 56,preferably to the eye thereof, as shown in FIGS. 3 and 4, whereby air isdrawn from chamber 50 to fan 56. The air system, therefore, becomes asubstantially closed system. If necessary, a suitable air inlet may beprovided either in the fan or in the casing 50, but it is believed thatsuch will not be necessary, as I prefer a substantially closed airsystem, and for the additional reason that some air will find its waybetween the conveyor 52 and the lower end of the casing 50 and in chutes46 and 48.

As indicated in FIGS. 3 and 4, the main body of the a-ir issues from thehorizontal conduit portions 70 and 72 and moves horizontally, as shownby the arrows B in FIG. 3, due to the return conduits 86, Sil, 90 and92. This air carries the finer particles which are too light to droponto the belt. These liner particles are then mixed with the downwardlyfalling flakes as they fall through the chutes 46, 48, and some of themadhere to these akes. The principal reason for recirculation, however,is to cut down turbulence in the casing 50, as only about 1% or less ofthe material is recirculated.

The mat A4 which is produced by this system `and method preventstelegraphing through the face veneer, plastic overlay, or paper covers,if one of them is used, even though the same is only 1/32 inch thick.

The term telegraphing in this art indicates the protrusion through theveneer, plastic overlay, or paper of one or more of the wood particles.The particles as laid in accordance with the above described inventiontend to lie on the belt 52 with their longitudinal axes in alignmentwith the direction of movement of the belt.

The mat, such as that shown at A4, after being subjected to a pressingoperation, is cut transversely to proper length, to form panels, and maythen be subjected to a veneering machine and finished with a lacquercoating step involving a pigmented toner and a low built mat finish ofthe type used by furniture manufacturers.

Panels reserved for plastic overlaying, of three-ply construction asdescribed herein, may be supplied to a commercial fabricator whosupplies the plastic overlay face, such as 1&6 inch, more or less, of aFormica overlay, and about 0.020 inch thick phenolic backing using aurea glue. Low pressures were used, in accordance with normal procedure,to reduce the possibility of the core particles telegraphing through theplastic overlay face or paper covers.

It is the usual practice in the manufacture of panels of the type hereindescribed, after the steps of compressing and cutting, to follow withplastic overlaying, veneering, or paper covers, and then to apply testsin accordance with the end use for which Ithe panels have beenmanufactured, i.e., furniture core stock, or plastic overlay corestock,or corestock to be used in the building industry. The initial moisturecontent of all boards to be so used should range from 5% to 7%.

Building test strength depends upon variations in thicknesses of thecores amd faces, i.e. the portion indicated by A3 `and faces A1, A1,respectively, and different species of wood used. There are many othervariations which must be considered also that will determine strength,such as the amount of compression used, and -the amount of adhesiveused.

The term wood particles includes in major proportions wood products, butmay also include in minor proportions various amounts of variousmineral, vegetable, or animal particles mixed with a major proportion ofwood particles.

The size of wood particles has been shown larger than actual size in thedrawings for illustrative purposes. Generally speaking, the particlesize will be controlled in accordance with the use -to -be made of theboards, as well as by lother variables, such as economy, source ofsupply, etc.

The above description and drawings ydisclose a single embodiment of theinvention, and specific language has been employed in describing theseveral figures. It will, nevertheless, be understood that nolimitations of the scope of the invention are thereby contemplated, andthat various alterations and modifications may be made such as wouldoccur to one skilled in the art to which the invention relates.

I claim:

Apparatus comprising a mat Iforming unit, means for delivering particlesto said unit to fall by gravity therethrough, means for directingvertically spaced streams of air horizontally from adjacent the centerof saidV unit toward each end thereof to effect size distribution ofsaid particles, means -for recirculating air from each end of said unitand means for adjusting the relationship of said vertically spacedhorizontal air streams with respect to the falling particles deliveredto said unit.

References Cited in the le of this patent UNITED STATES PATENTSTifchmars'h June 20, 192.1 Doxran May 28, 1935 Stoner Nov. 26, 1940Duncan Sept. 9, 1941 lo

